On Thu, 27 May 2010, Alan Cox wrote: > > Rather than continue going around in circles, let's agree that what the > > Android people want is a new version of forced suspend -- not a > > I don't think this is true. I think that is the root of the problem. Of course it's true. Just ask Arve -- he wants opportunistic suspend and it _is_ a variant of forced suspend. Ergo he wants a new type of forced suspend. Maybe that's not what he _ought_ to want. Nevertheless, there are valid reasons for wanting it. > I don't disagree with the user experience they are trying to create or > the fact something is needed to make it possible (if it turns out we > can't already do it). > > Forced suspend is sticking stuff in running state into suspend > > Power management models (such as Thomas ARM box) which we know work are > 'when nothing is running' into suspend. > > So for me the real question on that side of this specific case is 'how > do you make sure those tasks are idle when you need them to be' > > QoS ? > Spanking them from user space ? > Drivers enforcing policy elements by blocking tasks ? Currently we use the freezer. But it is a blunt tool -- it freezes every user process. Also, it doesn't actually make processes unrunnable; it just arranges things so that when they do run, they immediately put themselves back to sleep. And the forced-suspend design relies on the fact that processes remain frozen throughout. If we leave some processes unfrozen and one of them somehow becomes runnable, that means we have to abort the forced suspend before the process is allowed to run. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
